wrap message trashing into simple transactions

trashing many messages at once inevitably overtaxes m$ exchange, and the
connection breaks. without any progress tracking, it would restart from
scratch each time, which would lead to a) it never finishing and b) many
copies of the messages in the trash.

full transactions as we do for "proper" syncing would be over the top,
as it's not *that* bad if some messages get duplicated in the trash. so
we record only the messages for which trashing completed, thus allowing
some overlap between the attempts.

TODO

@@ -1,8 +1,5 @@
 f{,data}sync() usage could be optimized by batching the calls.
 
-add some marker about message being already [remotely] trashed.
-real transactions would be certainly not particularly useful ...
-
 make SSL (connect) timeouts produce a bit more than "Unidentified socket error".
 
 uidvalidity lock timeout handling would be a good idea.

src/sync.c

@@ -175,6 +175,7 @@ typedef struct {
 	driver_t *drv[2];
 	const char *orig_name[2];
 	message_t *new_msgs[2];
+	int_array_alloc_t trashed_msgs[2];
 	int state[2], ref_count, nsrecs, ret, lfd, existing, replayed;
 	int new_pending[2], flags_pending[2], trash_pending[2];
 	int maxuid[2]; /* highest UID that was already propagated */
@@ -799,7 +800,7 @@ load_state( sync_vars_t *svars )
 				}
 				if ((c = buf[0]) == '#' ?
 				      (t3 = 0, (sscanf( buf + 2, "%d %d %n", &t1, &t2, &t3 ) < 2) || !t3 || (t - t3 != TUIDL + 3)) :
-				      c == '(' || c == ')' || c == '{' || c == '}' || c == '!' ?
+				      c == '(' || c == ')' || c == '{' || c == '}' || c == '[' || c == ']' || c == '!' ?
 				        (sscanf( buf + 2, "%d", &t1 ) != 1) :
 				        c == '+' || c == '&' || c == '-' || c == '|' || c == '/' || c == '\\' ?
 				          (sscanf( buf + 2, "%d %d", &t1, &t2 ) != 2) :
@@ -816,6 +817,10 @@ load_state( sync_vars_t *svars )
 					svars->newuid[M] = t1;
 				else if (c == '}')
 					svars->newuid[S] = t1;
+				else if (c == '[')
+					*int_array_append( &svars->trashed_msgs[M] ) = t1;
+				else if (c == ']')
+					*int_array_append( &svars->trashed_msgs[S] ) = t1;
 				else if (c == '!')
 					svars->smaxxuid = t1;
 				else if (c == '|') {
@@ -1920,6 +1925,11 @@ flags_set_p2( sync_vars_t *svars, sync_rec_t *srec, int t )
 	}
 }
 
+typedef struct {
+	void *aux;
+	message_t *msg;
+} trash_vars_t;
+
 static void msg_trashed( int sts, void *aux );
 static void msg_rtrashed( int sts, int uid, copy_vars_t *vars );
 
@@ -1927,6 +1937,7 @@ static void
 msgs_flags_set( sync_vars_t *svars, int t )
 {
 	message_t *tmsg;
+	trash_vars_t *tv;
 	copy_vars_t *cv;
 
 	if (!(svars->state[t] & ST_SENT_FLAGS) || svars->flags_pending[t])
@@ -1938,14 +1949,18 @@ msgs_flags_set( sync_vars_t *svars, int t )
 	    (svars->ctx[t]->conf->trash || (svars->ctx[1-t]->conf->trash && svars->ctx[1-t]->conf->trash_remote_new))) {
 		debug( "trashing in %s\n", str_ms[t] );
 		for (tmsg = svars->ctx[t]->msgs; tmsg; tmsg = tmsg->next)
-			if ((tmsg->flags & F_DELETED) && (t == M || !tmsg->srec || !(tmsg->srec->status & (S_EXPIRE|S_EXPIRED)))) {
+			if ((tmsg->flags & F_DELETED) && !find_int_array( svars->trashed_msgs[t].array, tmsg->uid ) &&
+			    (t == M || !tmsg->srec || !(tmsg->srec->status & (S_EXPIRE|S_EXPIRED)))) {
 				if (svars->ctx[t]->conf->trash) {
 					if (!svars->ctx[t]->conf->trash_only_new || !tmsg->srec || tmsg->srec->uid[1-t] < 0) {
 						debug( "%s: trashing message %d\n", str_ms[t], tmsg->uid );
 						trash_total[t]++;
 						stats();
 						svars->trash_pending[t]++;
-						svars->drv[t]->trash_msg( svars->ctx[t], tmsg, msg_trashed, AUX );
+						tv = nfmalloc( sizeof(*tv) );
+						tv->aux = AUX;
+						tv->msg = tmsg;
+						svars->drv[t]->trash_msg( svars->ctx[t], tmsg, msg_trashed, tv );
 						if (check_cancel( svars ))
 							goto out;
 					} else
@@ -1982,13 +1997,17 @@ msgs_flags_set( sync_vars_t *svars, int t )
 static void
 msg_trashed( int sts, void *aux )
 {
+	trash_vars_t *vars = (trash_vars_t *)aux;
 	DECL_SVARS;
 
 	if (sts == DRV_MSG_BAD)
 		sts = DRV_BOX_BAD;
-	if (check_ret( sts, aux ))
+	if (check_ret( sts, vars->aux ))
 		return;
-	INIT_SVARS(aux);
+	INIT_SVARS(vars->aux);
+	debug( "  -> trashed %s %d\n", str_ms[t], vars->msg->uid );
+	Fprintf( svars->jfp, "%c %d\n", "[]"[t], vars->msg->uid );
+	free( vars );
 	trash_done[t]++;
 	stats();
 	svars->trash_pending[t]--;
@@ -2008,8 +2027,10 @@ msg_rtrashed( int sts, int uid ATTR_UNUSED, copy_vars_t *vars )
 		free( vars );
 		return;
 	}
-	free( vars );
 	t ^= 1;
+	debug( "  -> remote trashed %s %d\n", str_ms[t], vars->msg->uid );
+	Fprintf( svars->jfp, "%c %d\n", "[]"[t], vars->msg->uid );
+	free( vars );
 	trash_done[t]++;
 	stats();
 	svars->trash_pending[t]--;
@@ -2105,6 +2126,8 @@ sync_bail( sync_vars_t *svars )
 {
 	sync_rec_t *srec, *nsrec;
 
+	free( svars->trashed_msgs[M].array.data );
+	free( svars->trashed_msgs[S].array.data );
 	for (srec = svars->srecs; srec; srec = nsrec) {
 		nsrec = srec->next;
 		free( srec );